Transcript ppt
ECEN4533 Data Communications Lecture #13 6 February 2013 Dr. George Scheets Read: 2.4 Problems: 2.1, 2.3, Web 4.2 Design #1 due 8 February (Async DL) Late = -1 per working day Quiz #1 < 11 February (Async Distance Learning) Corrected quizzes due 13 February (Live) ECEN4533 Data Communications Lecture #14 8 February 2013 Dr. George Scheets Problems: Web 4, 5, & 6 Design #1 due 8 February (Async DL) Late = -1 per working day Quiz #1 < 11 February (Async Distance Learning) \ Corrected quizzes due 13 February (Live) Exam #1: 22 February (Live), Various Protocols Ethernet #1 on the wired LAN Exceptions in some Data Centers Had plenty of competition 'til mid-90's Moving into MAN & WAN LAN frame is encapsulated Frame Relay Introduced commercially in 1990 Has its own Layer 2 Header Format In early 90's • Ethernet, Token Ring, FDDI common • IP not yet dominant (Novell common) Various Protocols ATM Hot protocol in mid 90's Complex compared to Frame Relay Meant to haul all types of traffic 5 Classes of Service Derided But as too Complex by Internet Fanatics now Internet is being asked to move everything Internet becoming more complex Various Protocols Internet Hot protocol in 2000's Commodity Internet Treats all traffic the same Corporate Internet Becoming more complex • DiffServ: Enables Priorities Not Used on Commodity Internet • Multi-Protocol Label Switching Enables Virtual Circuits Internet Traffic Growth source: "The Road to 100G Deployment", IEEE Communications Magazine, March 2010 Internet Traffic source: http://www.sandvine.coms 2008 - 2009 Comparison 2011 Internet Traffic Profile Source: http://www.sandvine.com/downloads/documents/ 2011 Global Internet Phenomena Report.pdf 2011 Internet Traffic Profile Source: http://www.sandvine.com/downloads/documents/ 2011 Global Internet Phenomena Report.pdf ISP Router Overload Source: 1 October 2007 Network World Fall 2011 Level3 BGP entries 375,550 IPv4 7,210 IPv6 Peak Traffic 8.0 Tbps IPv4 500 Mbps IPv6 Router Operates at OSI Layers 1-3 Communicate with adjacent Routers Exchange "Hello" packets every 10 or so seconds Exchange Routing info immediately upon "Hello" failure general updates several times a day independent of traffic Use Routing info to generate a Hierarchical Routing Table Example) ISP Backbone Routers Must know how to get to ibm.ucc.okstate.edu Example) OSU Campus Backbone Routers Must know how to get to ibm.ucc.okstate.edu Switched Ethernet R PC PC Switched Hub Pr Switched Hub PC PC PC PC Switched Hub Switched Hub PC PC Packet formatting same as before. Only the Printer will see packets from the PC. Switched Ethernet PC R PC Pr Switched Hub PC PC PC PC Switched Hub Switched Hub PC PC Packets need to cross a network boundary. Ex) Leased Lines Suppose: *BW available in 64 Kbps chunks (64, 128, 192, 256, 320, 384, 448, etc.) *Maximum load (traffic/BW) = 50% 320 Kbps Carrier Leased Line Network OKC Traffic Matrix (Bursty Data) From/To 256 Kbps OKC DET NYC OKC - 144 76 DET 88 - 28 NYC 112 34 - Detroit 128 Kbps NYC Router Ex) Leased Lines Suppose: *BW available in 64 Kbps chunks (64, 128, 192, 256, 320, 384, 448, etc.) *Maximum load (traffic/BW) = 50% Detroit 384 Kbps Carrier Leased Line Network OKC 320 Kbps From/To OKC DET NYC OKC - 144 76 DET 88 - 28 NYC 112 34 - NYC Router Ex) Leased Lines with Internet thru OKC Detroit ISP 640 Kbps OKC Carrier Leased Line Network NYC From/To OKC DET NYC ISP OKC - 144 76 60 DET 88 - 28 50 NYC 112 34 - 40 ISP 110 100 90 - Router Ex) Commodity Internet Corporate Connectivity Detroit 384 Kbps OKC 448 Kbps ISP Network 320 Kbps NYC Router From/To OKC DET NYC OKC - 144 76 DET 88 - 28 NYC 112 34 - Ex) Commodity Internet Corporate & Internet Connectivity Detroit 576 Kbps OKC From/To OKC 640 Kbps DETRouter NYC ISP ISP Network 448 Kbps NYC OKC - 144 76 60 DET 88 - 28 50 320/280 I/O @ OKC → 640 Kbps NYC 112 34 - 40 194/186 I/O @ NYC → 448 Kbps ISP 110 100 90 278/166 I/O @ DET → 576 Kbps - Virtual Circuit Backbone Server LAN LAN VC #2 PC VC #1 VC Switch Suppose we need to connect to three LAN's. LAN PC Ex) Frame Relay, ATM, MPLS, Carrier Ethernet Corporate Connectivity Detroit 384 Kbps OKC Carrier Frame Relay, ATM, Ethernet, or MPLS Internet Network. 576 Kbps 320 Kbps NYC From/To OKC DET NYC OKC - 144 76 DET 88 - 28 NYC 112 34 - OKC Outbound = 220 +28 +34 Kbps OKC Inbound = 200 + 28 +34 Kbps Leased Line Size > 2*282 = 564 Kbps Leased Line = 576 Kbps minimum. Ex) Carrier Ethernet, FR, ATM, MPLS Corporate & Internet Connectivity Detroit 576 Kbps ISP 640 Kbps OKC Router From/To OKC DET 960 Kbps Carrier Ethernet, ATM, MPLS, or FR Network 448 Kbps NYC NYC ISP OKC - 144 76 DET 88 - 28 NYC 112 34 - ISP 110 100 90 OKC FR Leased Line must handle 50 NYC & Det traffic ↔ Internet, 40 OKC ↔ corporate, and - Detroit/NYC pass-thru traffic. 60 Leased Line at OKC ↔ FR Net Outbound OKC→Det 144 OKC→NYC 76 Det→NYC 28 NYC→Det 34 ISP→Det 100 ISP→NYC 90 From/To OKC DET Inbound Det→OKC 88 Det→NYC 28 ISP Det→ISP 50 NYC→OKC 112 OKC NYC→Det 34 NYC→ISP 40 Detroit NYC NYC ISP OKC - 144 76 60 DET 88 - 28 50 NYC 112 34 - 40 ISP 110 100 90 - Total Outbound = 472 Kbps Total Inbound = 352 Kbps Leased Line Size > 944 Kbps Leased Line = 960 Kbps minimum. Circuit Switched TDM Leased Line Cross-Connect 100 Mbps Trunk ?? 1.54 Mbps Connections P(Access Line is Active) = 10% Trunk Bandwidth is assigned based on peak input rates. Can support 64 access lines. Queue Length 100,000,000 bps output trunk 100,000,001 bps average input Average Input rate > Output rate Queue Length builds up (without bound, in theory) Queue Length 100,000,000 bps output trunk 99,999,999 bps average input Average Input rate < Output rate Queue Length not infinite... ...but very large Queue Length @ 100% Load Output capacity = 7 units Input = 7 units on average (two dice rolled) t1: input = 4, output = 4, queue = 0 t2: input = 5, output = 5, queue = 0 t3: input = 4, output = 4, queue = 0 t4: input = 7, output = 7, queue = 0 t5: input = 11, output = 7, queue = 4 t6: input = 10, output = 7, queue = 7 t7: input = 6, output = 7, queue = 6 t8: input = 5, output = 7, queue = 4 t9: input = 8, output = 7, queue = 5 t10: input = 11, output = 7, queue = 9 This queue will tend to get very large over time. Queue Length @100% Load Will tend to increase w/o Bound. 4000 3 3.40910 queue5 j2000 0 0 0 0 2 10 4 10 5 5 j 5 6 10 8 10 5 1 10 6 110 5 6 2000 3 1.98310 queue5 j1000 0 0 0 0 2 10 5 4 10 5 j 5 6 10 5 8 10 5 1 10 6 110 6 Packet Switched StatMux Router or Switch 100 Mbps Trunk ?? 1.54 Mbps Connections P(Access Line is Active) = 10% Trunk Bandwidth assigned based on average input rates. Can theoretically support 649 access lines. Note if all inputs active, input = 999.5 Mbps Probability Density Functions A Histogram is an estimate of the PDF Important PDF's for Networking Gaussian Very common in the Real World Binomial Individual Experiment has 2 states Experiment results are Independent Interested in # of successful experiments, not specific order Exponential Not a bad model for packet sizes Poisson 1995 OSU Backbone Packet Histogram Looks somewhat exponential. 2004 OSU Backbone Packet Histogram Still looks sort of exponential, but less so than before, IM Traffic Message Size Actual Traffic - Packet Size PDF 0.08 0.07 0.06 Probability 0.05 0.04 0.03 0.02 0.01 0 0 20 40 60 80 Bytes 100 120 140 160 Traffic in 0.1 second intervals